The use of simvastatin for the prevention of gallstones in the lithogenic prairie dog model

Background: Surgery for morbid obesity is rapidly increasing. Patients undergoing bariatric surgery are prone to gallstone development during the rapid weight loss. These patients are often given medications such as ursodeoxycholic acid to prevent gallstone formation; however, these medications are often poorly tolerated by patients, who subsequently discontinue them. We performed a study in a lithogenic animal model to assess the effectiveness of a potential alternate medication for gallstone prevention. Methods: 20 male prairie dogs were randomly separated into 2 groups and fed a lithogenic diet for 28 days. The study group animals were given 2.5 mg of the HMG-CoA reductase inhibitor simvastatin. Total cholesterol and triglycerides were measured and an open cholecystectomy was performed on each animal at the conclusion of the study period. The gallbladder was visually inspected for gallstones and microscopic biliary cholesterol crystal formation. Results: There was a decrease of 36% in the total cholesterol of the study animals compared to controls. The animals treated with simvastatin showed gallstone formation in 5/10 (50%) of animals, compared with 6/10 (60%) of control animals. The study animals demonstrated microscopic cholesterol crystal formation in 80%, identical to the number found in the control animals. Conclusion: Despite a reduction in cholesterol, simvastatin prevented neither gallstone formation nor biliary cholesterol crystals in this animal model. Given the rapid increase in the number of bariatric surgical procedures coupled with the poor tolerance of ursodeoxycholic acid, viable alternatives should continue to be sought for these patients.